The hydraulic transfer method is a method for forming a decorative layer, by coating an activator, which is capable of making a print pattern in a fluidized state by dissolving or swelling said print pattern, onto the print pattern of a transfer film for hydraulic transfer, composed of a water-soluble film having a non-water soluble print pattern (print design) on the surface, after that, floating this transfer film for hydraulic transfer on water so that the print pattern surface becomes the upper surface side, and by pushing in a molded article of an object to be transferred, from the upper surface thereof, at a stage when the print pattern layer in a fluidized state is spread on water surface, to transfer the print pattern in a fluidized state and spread state, by utilizing hydraulic pressure; and such a hydraulic transfer method has already been known. In addition, the present applicant has proposed a hydraulic transfer method superior in adhesion of the decorative layer to the object to be transferred, and rubfastness, even not using a conventional topcoat, by coating an activator composed of a UV ray hardening-type composition, integrating ink for a print pattern and the above UV ray hardening-type composition, and then hardening using UV ray (for example, refer to PATENT LITERATURE 1, 2 or the like).
Here, the activator to be coated on the above transfer film for hydraulic transfer is not the one having such specifications that particularly limit a material of the object to be transferred, and practically, in view of quality such as adhesion or the like of the decorative layer, as the object to be transferred, such a resin substrate has been adopted that has easy adhesion and is superior in mass productivity (less defect occurrence), and thus, among plastic-type materials with poor adhesion•poor adhesiveness, a polyolefin-type material with particularly poor adhesion•poor adhesiveness has been a state difficult to be applied. That is, in the case where a material of the object to be transferred is non-polyolefin-type plastic, for example, an ABS resin, a polycarbonate resin, a polyvinylchloride resin, an acrylic resin or the like, a conventional activator is possible to form a practically satisfactory decorative layer with high adhesion, on the surface of a molded article, however, in the case where the material of the molded article is a polyolefin-type resin such as polyethylene, polypropylene, adhesion of the decorative layer transferred was extremely low, as compared with the above ABS resin or the like, and thus improvement of adhesion has conventionally been a problem.
To solve the above problem, such a method has conventionally been proposed that includes an adhesion furnishing component in the activator (for example, refer to PATENT LITERATURE 3).
In the above PATENT LITERATURE 3, as the activator called a primer, such an activator has been disclosed that is coated on the transfer film for hydraulic transfer dispersed with a binder resin composed of a graft-copolymer consisting of 5 to 50% by weight of an alkoxy-(poly)alkylene glycol.mono(metha)acrylate, 5 to 50% by weight of a chlorinated polypropylene resin, and 0 to 90% by weight of a vinyl compound having a polymerizable unsaturated group, in an organic solvent.
However, because this activator includes the binder resin composed of a chlorinated polyolefin, a solvent such as toluene is essential to disperse the chlorinated polyolefin, and thus including of such a solvent in the activator has a problem of difficulty in adjustment of ink activation of the print pattern, and application of the activator including the chlorinated polyolefin, which has been known effective in view of adhesion to the polyolefin-type substrate, has not necessarily been superior in productivity.
In addition, in the case of using a UV ray hardening-type (UV) activator having a UV ray hardening-type composition as a component, in particular, as the activator, dissolving power of the UV ray hardening-type activator and the chlorinated polyolefin is poor, and additional addition of a solvent component to the UV ray hardening-type activator, aiming at dissolving the chlorinated polyolefin, not only makes difficult to adjust ink activation of the print pattern but also inhibits integration in perfect harmony of ink and the UV ray hardening-type activator component, resulting in being impossible to provide a decorative layer of a topcoat-less superior in adhesion and rubfastness, due to generation etc. of decrease in film strength or adhesion of the decorative layer after UV ray hardening, and thus it has not been applicable to a method where an adhesion improvement component is made present internally in the activator.
In addition, in the case of including an isocyanate component as an adhesion furnishing component, even when the addition to the activator is possible, a water-soluble film (usually polyvinylalcohol) of the transfer film for hydraulic transfer, and the isocyanate component react and generate a trouble in finishing of the decorative layer of the transfer products, such as causing residue removing of coating of the water-soluble film after transfer, therefore it was not enough to simply add the adhesiveness furnishing component to the activator.
Further, in any of the hydraulic transfer methods, in the case of applying the activator dedicated to the polyolefin-type substrate, each time when the object to be transferred changes from the olefin-type substrate to a non-olefin-type substrate (or in an opposite way thereof), exchange of the activator is required, which has also caused limitation of productivity.
In addition, in PATENT LITERATURE 4, there has been disclosed that, by using a protective coating film, where a hydroxyl group-containing resin composition obtained by graft-copolymerization of a chlorinated polypropylene-type resin and an acryl-polyol component consisting of cyclohexyl methacrylate, t-butyl methacrylate and hydroxyethyl methacrylate, is hardened by a polyisocyanate-type hardening agent, as the protective coating film onto the print pattern transferred, the protective coating film having superior adhesion can be obtained at both of the polypropylene-type resin molded article and the print pattern layer.
However, although the method for coating the protective coating film provides expectation of effect of adhesive holding of the print pattern to the substrate, due to enclosing the print pattern transferred together with the substrate by the protective coating film, it cannot be applied to the hydraulic transfer method not requiring the protective coating film (topcoat), as in PATENT LITERATURE 1 and PATENT LITERATURE 2 using the UV ray hardening-type activator having the UV ray hardening-type composition as a component, therefore, it has not been a method widely applicable to the hydraulic transfer method.
In addition, as another conventional method, there has been a method for forming a decorative layer by hydraulic transfer after forming the surface treatment layer (undercoat layer), by coating the surface treatment agent (what is called a primer agent) including the chlorinated polyolefin at the surface of an object to be transferred (for example, refer to PATENT LITERATURE 5).
In the above PATENT LITERATURE 5, there has been disclosed a method for forming a decorative layer which is hydraulic transferred at an undercoat layer surface by forming the undercoat layer using a coating material based on a two component urethane modified chlorinated polyolefin resin as a primer.
Such a chlorinated polyolefin-type primer has widely been used commonly without limiting to hydraulic transfer, and a reactive urethane-type or the like, which is obtained by reacting a polyol with isocyanate has been known (for example, refer to PATENT LITERATURE 6), however, in any of them, an undercoat layer formed generally has not a little tackiness (tackiness), which tends to catch dust or the like at the surface of the undercoat layer before a transfer step in such a state, therefore, there has been a problem in view of securing productivity (securing yield) or securing quality stability, such that work in a clean room is necessary for countermeasure thereof. In addition, as a method for decreasing tackiness of the undercoat layer, there is a heating treatment method of the undercoat layer, however, it has been a problem of cost increase and productivity decrease, caused by increase in the heating treatment step.
In addition, as still another conventional method, there are various methods such as conventional flame treatment, corona treatment, plasma treatment, ITRO treatment for forming a nano-level silicon oxide film at the surface of an object to be coated via oxidizing flame by flame burner, and the like, however, there has been a problem of productivity and cost increase, due to requirement of special equipment.
As described above, in order to solve a problem of improving adhesion between an object to be transferred composed of a polyolefin-type resin such as polypropylene, and a decorative layer having a print pattern transferred, various methods have been proposed, however, a method for decorating by hydrolytic transfer, with high adhesion, at the polyolefin-type substrate, which has generally poor adhesiveness, is still not sufficient.
Accordingly, a hydraulic transfer method, that is capable of hydraulic transfer decoration having high adhesion onto an olefin-type substrate, which is an object to be transferred with poor adhesion, and also has superior productivity, has been required.